An X-ray negative is prepared by exposing a sheet of X-ray sensitive film to a source of X-ray radiation with the object of interest placed in alignment between the film and the X-ray source. The object being X-rayed absorbs the radiation non-uniformly depending on various criteria, such as type of material and material thickness or density. The radiation which is transmitted through the object to the film, accordingly, is also non-uniform and results in a pattern of light and dark areas on the developed film (negative) corresponding to the absorptivity of the object. With proper training, the X-ray negative can be interpreted to reveal characteristics of the object not normally visible to the human eye.
Although X-rays have a wide variety of industrial uses, they are probably most extensively used in the field of medicine. Regardless of the application of X-rays, it is helpful in interpreting an X-ray negative to know the orientation of the object X-rayed and the orientation of the film when exposed to the radiation. It has therefore been the typical practice for X-ray technicians to place X-ray opaque objects, such as lead letters, on the X-ray film holder during exposure, so that the "shadow" of the letters will appear on the X-ray negative and thereby give a permanent visual indication of film and object orientation at the time the X-ray was made. It is also often desirable to provide an indication of the X-ray technician who prepared the X-ray. Accordingly, lead letters or numbers corresponding to individual X-ray technicians or other information can be placed on the film holder in the same manner described above. The use of individual lead letters and the lack of a convenient method for attaching the letters to the film holder makes this method of marking X-rays awkward since the letters can be lost or fall off the film holder when the film holder is in a non-horizontal orientation.
The foregoing problems were recognized in U.S. Pat. No. 4,127,774 (incorporated herein by reference). That patent discloses an X-ray marker which includes lead indicia to provide an indication of right or left orientation and operator initials. A quantity of mercury contained in an asterisk-shaped cavity provides an indication of vertical or horizontal orientation. Furthermore, the marker device is securable to film holders by a multiplicity of suction cups on the back of the marker device. That device is not entirely satisfactory because of its size. Moreover, since multiple suction cups are used, a relatively large flat surface is required to attach the marker device thereto and adhesion of the marker device can be undependable despite the multiple suction cups and corresponding surface area covered by the cups.
Other patents which may be relevant to the subject matter of the present application include U.S. Pat. Nos. 1,800,218 and 1,883,791 (both incorporated herein by reference). Although those patents disclose suction cup devices, they do not relate to X-ray marker devices, and, therefore, are not material to the subject matter of the present invention.